Features and build
The new Sigma 105mm f/2.8 lens has a completely new lens construction, with 16 elements in 11 groups compared to the 11 elements in 10 groups used for the old version.
These include two SLD (Special Low Dispersion) elements to correct spherical aberration, chromatic aberration and curvature, and super multi-layer coatings on the front and rear elements to reduce flare and ghosting. Unlike the old 105mm version, focusing is internal, using a floating system that moves two lens groups to adjust focus. This avoids the extreme extension of the lens for close focusing that saw the previous lens almost double in size.
The optical stabilisation system appears to be the same as that featured on the recent Sigma 150mm macro lens, among others, and, according to Sigma, it offers a 4-stop benefit in shake reduction. While most precise close-up work should be performed with a steady tripod, when you are shooting handheld any form of stabilisation is very useful.
The stabilisation has two settings, comprising a full dual-axis mode and a single-axis mode for panning. The front filter thread is larger by 4mm, being 62mm in diameter, and it sits much closer to the front element. This should improve optical quality when using a filter. Sigma has done away with the push-pull AF/manual-focus selection of the old model and opted for a simple switch on the new 105mm lens.
On the Nikon-mount version we tested, the focus ring allows manual-focus override when AF is selected on the lens and on the camera.
However, when manual focus is selected on the camera, the AF switch on the lens becomes inactive. The aperture ring that featured on the previous Nikon version has also been omitted. The focus ring sits at the very front of the lens and is fractionally smaller than on the previous model, but it is still broad enough for easy operation.
The focus window contains three readings of distance, in feet, metres and magnification, which is handy for precise reproductions. A focus range limiter switch usefully allows three options for full 31.2cm to infinity, 45cm to infinity and 31.2cm to 45cm to avoid excessive hunting.
The lens comes with a 55mm lens hood, which, when not in use, can be reversed for storage. With the hood reversed it sits snug to the barrel and covers the focus ring and window, but still allows the lens to be comfortably held and used in autofocus.
When used on entry-level cameras the new 105mm lens feels large and bulky in a way the previous model did not. However, with its current specification and price, the lens will probably be used on mid-range or high-end bodies. Here it feels better balanced, and looks very similar to Nikon’s 105mm f/2.8G AF-S VR Micro-Nikkor, which is available at a slightly cheaper street price than the Sigma 105mm.
